1. Field of the Invention
The present invention relates to a parking ramp for a Hard Disk Drive (HDD). More particularly, the invention relates to a parking ramp providing sufficient driving margin during an unloading operation to minimize the area allocated on a disk for the parking ramp.
This application claims the benefit of Korean Patent Application No. 10-2005-0124374, filed on Dec. 16, 2005, the subject matter of which is hereby incorporated by reference.
2. Description of the Related Art
Hard disk drives (HDDs) are commonly used within various host devices, such as personal computers (PCs), as data storage devices. In general operation, HDDs allow data to be written to and read from recording medium (e.g., a disk having a surface subject to variation in its magnetic properties) using a magnetic read/write head. Data is stored on conventional disks in terms of bits per inch (BPI)—a recording density defined in relation to the disk's rotational direction, and tracks per inch (TPI)—a recording density defined in relation to the disk's radial direction. Significant research and development efforts are currently being expended to increase data recording density according to both of these definitions. Additionally, commercial demands are motivating the design and manufacture of increasingly small HDDs. The miniaturization of HDDs, together with demands for higher data recording densities, require ever finer and more precise mechanisms within HDD structures. These demands also necessitate the efficient use of available disk space.
The read/write head within the HDD is typically moved over the recording surface of the disk using an actuator. As the HDD operates, the disk rotates at a constant speed and the read/write head floats at a predetermined height over the surface of the rotating disk. In this state, the read/write head is moved to a desired position during a read/write operation by the actuator. However, when power to the HDD is interrupted (e.g., turned OFF), the read/write head must be withdrawn from over the recording surface of the disk before it can be placed in a resting state. This type of operation is commonly referred to as an unloading/parking operation, as the read/write head is unloaded from the recording surface of the disk and safely parked in a designated location. Parking of the read/write head is usually accomplished in relation to a so-called parking ramp—a structure and/or location adapted to receive a parked read/write head.
The apparently simple task of parking a read/write head is actually fairly involved. As the disk rotates, a predetermined volume of air flow over the surface of the disk induces a pressure difference which tends to move the read/write head towards the disk surface. This downward pressure is balanced by a mechanical spring force (loading) imparted by a suspension supporting the head. When power is no longer applied to the HDD and the disk stops rotating, the combined forces that cooperate to precisely float and position the read/write head over the recording surface of the disk must be altered to rapidly move the read/write head into a parked position.
The parking ramp structure has long been used to help facilitate the unloading/parking operation. Parking ramps have a ramped (or inclined) profile adapted to receive a read/write head. The shape and size of the parking ramp must be carefully designed in relation an available driving margin applied to the actuator during an unloading/parking operation. That is, as the inclination of a parking ramp's inclined surface decreases, the driving margin for the unloading/parking operation is generally improved. Providing a larger voice coil motor to drive the actuator during an unloading/parking operation is another way of increasing driving margin.
However, as ever more compact HDDs are developed for mobile use, ones ability to provide larger voice coil motors and longer, less steeply inclined parking ramps become very restricted. There simple isn't enough room within the HDD. This restriction presents a real problem as relatively steep inclinations for the parking ramp and limited driving margin may result is situations where the read/write head can not be moved completely off the recording surface of the disk. This is particularly true since smaller HDDs have smaller disks. As a result, disks must often be provided with relatively large safe zones adapted to receive contact from a “parked” read/write head. This safe zone area may not be used to record data and the storage capacity of the HDD is restricted.